On 9 December 2010 18:33, David Boxenhorn <david@lookin2.com> wrote:

What do you mean by indexing?On Thu, Dec 9, 2010 at 7:30 PM, Sébastien Druon <sdruon@spotuse.com> wrote:

Thanks a lot for the answerWhat about the indexing when adding a new element? Is it incremental?Thanks againOn 9 December 2010 14:38, David Boxenhorn <david@lookin2.com> wrote:

How about a regular CF where keys are N@N ?

Then, getting a matrix row would be the same cost as getting a matrix column (N gets), and it would be very easy to add element N+1.

On Thu, Dec 9, 2010 at 1:48 PM, Sébastien Druon <sdruon@spotuse.com> wrote:Hello,For a specific case, we are thinking about representing a N to N relationship with a NxN Matrix in Cassandra.The relations will be only between a subset of elements, so the Matrix will mostly contain empty elements.We have a set of questions concerning this:- what is the best way to represent this matrix? what would have the best performance in reading? in writing?. a super column family with n column families, with n columns each. a column family with n columns and n linesIn the second case, we would need to extract 2 kinds of information:- all the relations for a line: this should be no specific problem;- all the relations for a column: in that case we would need an index for the columns, right? and then get all the lines where the value of the column in question is not null... is it the correct way to do?When using indexes, say we want to add another element N+1. What impact in terms of time would it have on the indexation job?Thanks a lot for the answers,Best regards,Sébastien Druon